Lipophilic drug compositions

ABSTRACT

The invention is directed to biologically active lipophilic compositions comprising a biologically active covalently attached to, or encapsulated within, a lipid. Preferably, a biologically active agent is both covalently attached to a lipid and encapsulated within a lipid composition. Preferred lipid components include triglycerides and fatty acids. The resulting composition is preferably adapted for oral administration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/134,329, filed Apr. 29, 2002, now U.S. Pat. No. 7,125,568 whichclaims the benefit of Provisional Application Ser. No. 60/314,092, filedAug. 23, 2001, both of which are incorporated herein by reference intheir entirety.

FIELD OF THE INVENTION

The invention relates to lipophilic drug compositions comprisingbiologically active agents in association with lipid components, methodsof making such compositions, and methods of using such compositions indrug delivery.

BACKGROUND OF THE INVENTION

The small intestine is the primary site for the absorption of drugsadministered orally. The most important element in the small intestinecontrolling absorption is the brush border membrane. It consists of aphospholipid bilayer into which polysaccharides and proteins areincorporated. This membrane creates absorption barriers to many polardrugs. A successful approach in the pharmaceutical industry has been tosynthesize prodrugs with increasing membrane permeability by esterifyingthe charge functionalities. For example, the prodrug of 6-azauridine forthe treatment of psoriasis and neoplastic disease is acetylated to form2′,3′,5′-triacetyl-6-azauridine in order to enhance bioavailability(Bloch, A., “The Design of Biologically Active Nucleoside”, Drug Design,Vol. IV, Chapter 8, Ariens, E J (Ed.), Academic Press, New York, 1973)(see also, Sinkula, A A, “Application of the Prodrug Approach toAntibiotics”, Pro-drug as Novel Drug Delivery Systems, pp 116-153,Higuchi, T. and Stella, V. (Eds.), ACS Symposium Series 14, AmericanCancer Society, Washington D.C., 1975; Yalkowski, S H and Morozowich,W., Drug Design, Vol.9, pp 121, Ariens, E J (Ed.), Academic Press, NewYork, 1980).

Pharmacokinetics measures the fate of drugs at the time of ingestionuntil elimination from the body. Bioavailability of a drug following anoral dosing is determined by its pharmacokinetics. At least threefactors dictate the efficacy of a drug: 1) the degree of drug absorptionthrough the GI tract; 2) the ease with which it becomes inactivated bythe biotransformation mechanisms of the liver and 3) the rate ofelimination from the body. The pharmaceutical industry usually focuseson drug formulation to increase drug efficacy by increasing drugabsorption. Hence, in recent years, there has been an explosion of drugencapsulation technology. The basic premise of drug encapsulation is toimprove drug delivery, lessen toxicity and improve efficacy.

The use of liposome technology as a drug delivery system has been aparticularly active area of research. These lipid vesicles are generallyneutral or zwitterionic lipids arranged into bilayers that entrap one(unilamellar) or more (multilamellar) spaces. In conventional liposomes,it is often difficult to entrap a high concentration of a drug. Further,in long-term storage, a drug entrapped within liposomes may leak. Thecost of pharmaceutical grade phospholipids used in liposomes is alsocost prohibitive. Thus, it is preferably for use in injectableformulations rather than for oral formulation (see M. Ostro,“Liposomes”, Marcel Dekker, New York, 1983).

There remains a need in the art for cost-effective methods of improvingdrug efficacy and bioavailability and lessening drug toxicity.

SUMMARY OF THE INVENTION

The present invention provides biologically active lipophiliccompositions, particularly solid compositions adapted for oraladministration. The lipophilic compositions of the invention exhibitimproved bioavailability and reduced toxicity as compared tonon-lipophilic parent drug compounds. The invention involves covalentlyattaching a lipid molecule to a biologically active agent and/orencapsulating a biological active agent within a lipid composition.Preferably, the lipid molecule covalently attached to the biologicallyactive agent is a non-amphipathic lipid, such as a triglyceride or afatty acid. Similarly, the encapsulating lipid composition is preferablynon-amphipathic. In a preferred embodiment, a biologically active agentis covalently attached to a C4-C30 fatty acid and then encapsulatedwithin a mixture of at least one triglyceride and at least one fattyacid. The linkage between the biologically active agent and the lipid ispreferably hydrolytically stable and enzymatically cleavable. Examplesof suitable linkages include ethers, thioethers, imides, amides,sulfonamides, phosphonamides, disulfides, and carbamides.

The biologically active agent can be, for example, peptide, protein,enzyme, small molecule drug, dye, nucleoside, oligonucleotide,oligosaccharide, polysaccharide, vaccine, cell, or a virus. In oneembodiment, the biologically active agent is the biologically activecore structure of a known group of structurally similar compounds havinga common biological activity, such as penicillins, floxins, ACEinhibitors, and the like. The biologically active core structure can bedetermined by analyzing the structurally similar compounds and selectingthe structural components shared by the structurally similar compounds,the shared structural components forming the biologically active corestructure.

The encapsulation of the biologically active agent can be readilyaccomplished by dissolving a first lipid composition (e.g., C4-C30 fattyacid) in a solvent, mixing the dissolved lipid with the biologicallyactive agent with sufficient mixing intensity to form an emulsifiedmixture, adding a second lipid composition (e.g., one or moretriglycerides) to the emulsified mixture while continuing to mix theemulsified mixture, solidifying the mixture, and drying the mixture toform a dry solid composition.

In another aspect, the present invention provides a biologically activelipophilic compound comprising a substituted or unsubstituted5-nitrothiazole covalently attached to a lipid molecule, for example,having the structure:

wherein L is a linkage, such as an amide linkage, R is hydrogen, alkyl,substituted alkyl, aryl, substituted aryl, heteroaryl, substitutedheteroaryl, heterocyclic, or substituted heterocyclic, and LIPID is aresidue of a C4-C30 fatty acid. The above-described 5-nitrothiazolederivative is useful for treating an infection in a mammal, such as aparasitic, bacterial, viral, or fungal infection.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying figures, wherein:

FIG. 1 illustrates the rate of degradation of aspirin and encapsulatedaspirin in sodium carbonate;

FIG. 2 illustrates the in-vitro bioavailability of NTZ and encapsulatedNTZ when subjected to dissolution;

FIG. 3 illustrates the pharmacokinetic profile of ivermectin from ahorse that was dosed with the Sterotex® encapsulated drug;

FIG. 4 is a freeze fracture electron micrograph taken at about 27Kmagnification of NTZ encapsulated in Sterotex®/palmatate;

FIG. 5 is a freeze fracture electron micrograph taken at 8.3Kmagnification of NTZ encapsulated in Sterotex®/palmatate;

FIG. 6 is a second freeze fracture electron micrograph taken at about8.3 K magnification of NTZ encapsulated in Sterotex®/palmatate;

FIG. 7 illustrates a method of synthesis for compound BA 3540;

FIG. 8 is a graph of the UV spectra for compound BA 3540;

FIG. 9 is a graph of the HPLC data for compound BA 3540; and

FIG. 10 illustrates the encapsulated compound BA 3540 coalescing withencapsulating fatty acid and triglyceride tails.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter. Thisinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein; rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the invention to thoseskilled in the art.

I. Definitions

The terms “functional group”, “active moiety”, “activating group”,“reactive site”, “chemically reactive group” and “chemically reactivemoiety” are used in the art and herein to refer to distinct, definableportions or units of a molecule. The terms are somewhat synonymous inthe chemical arts and are used herein to indicate the portions ofmolecules that perform some function or activity and are reactive withother molecules. The term “active,” when used in conjunction withfunctional groups, is intended to include those functional groups thatreact readily with electrophilic or nucleophilic groups on othermolecules, in contrast to those groups that require strong catalysts orhighly impractical reaction conditions in order to react (i.e.,“non-reactive” or “inert” groups). For example, as would be understoodin the art, the term “active ester” would include those esters thatreact readily with nucleophilic groups such as amines. Exemplary activeesters include N-hydroxysuccinimidyl esters or 1-benzotriazolyl esters.Typically, an active ester will react with an amine in aqueous medium ina matter of minutes, whereas certain esters, such as methyl or ethylesters, require a strong catalyst in order to react with a nucleophilicgroup.

The term “linkage” or “linker” is used herein to refer to groups orbonds that normally are formed as the result of a chemical reaction andtypically are covalent linkages. Hydrolytically stable linkages meansthat the linkages are substantially stable in water and do not reactwith water at useful pHs, e.g., under physiological conditions for anextended period of time, perhaps even indefinitely. Hydrolyticallyunstable or degradable linkages means that the linkages are degradablein water or in aqueous solutions, including for example, blood.Enzymatically unstable, degradable or cleavable linkages means that thelinkage can be degraded by one or more enzymes.

The term “alkyl” refers to hydrocarbon chains typically ranging fromabout 1 to about 24 carbon atoms in length, and includes straight andbranched chains. The hydrocarbon chains may be saturated or unsaturated.The term “substituted alkyl” refers to an alkyl group substituted withone or more non-interfering substituents, such as, but not limited to,C3-C6 cycloalkyl, e.g., cyclopropyl, cyclobutyl, and the like;acetylene; cyano; alkoxy, e.g., methoxy, ethoxy, and the like; loweralkanoyloxy, e.g., acetoxy; hydroxy; carboxyl; amino; lower alkylaminoand dialkylamino, e.g., methylamino; ketone; halo, e.g. chloro or bromo;phenyl; substituted phenyl, and the like.

“Alkoxy” refers to an —O—R group, wherein R is alkyl or substitutedalkyl, preferably C1-C6 alkyl (e.g., methoxy or ethoxy).

“Aryl” means one or more aromatic rings, each of 5 or 6 core carbonatoms. Multiple aryl rings may be fused, as in naphthyl or unfused, asin biphenyl. Aryl rings may also be fused or unfused with one or morecyclic hydrocarbon, heteroaryl, or heterocyclic rings.

“Substituted aryl” is aryl having one or more non-interfering groups assubstituents. For substitutions on a phenyl ring, the substituents maybe in any orientation (i.e., ortho, meta or para).

“Heteroaryl” is an aryl group containing from one to four N, O, or Satoms(s) or a combination thereof, which heteroaryl group is optionallysubstituted at carbon or nitrogen atom(s) with C1-6 alkyl, —CF₃, phenyl,benzyl, or thienyl, or a carbon atom in the heteroaryl group togetherwith an oxygen atom form a carbonyl group, or which heteroaryl group isoptionally fused with a phenyl ring. Heteroaryl rings may also be fusedwith one or more cyclic hydrocarbon, heterocyclic, aryl, or heteroarylrings. Heteroaryl includes, but is not limited to, 5-memberedheteroaryls having one hetero atom (e.g., thiophenes, pyrroles, furans);5 membered heteroaryls having two heteroatoms in 1,2 or 1,3 positions(e.g., oxazoles, pyrazoles, imidazoles, thiazoles, purines); 5-memberedheteroaryls having three heteroatoms (e.g., triazoles, thiadiazoles);5-membered heteroaryls having 3 heteroatoms; 6-membered heteroaryls withone heteroatom (e.g., pyridine, quinoline, isoquinoline, phenanthrine,5,6-cycloheptenopyridine); 6-membered heteroaryls with two heteroatoms(e.g., pyridazines, cinnolines, phthalazines, pyrazines, pyrimidines,quinazolines); 6-membered heretoaryls with-three heteroatoms (e.g.,1,3,5-triazine); and 6-membered heteroaryls with four heteroatoms.

“Substituted heteroaryl” is heteroaryl having one or morenon--interfering groups as substituents.

“Heterocycle” or “heterocyclic” means one or more rings of 5, 6 or 7atoms with or without unsaturation or aromatic character and at leastone ring atom which is not carbon. Preferred heteroatoms include sulfur,oxygen, and nitrogen. Multiple rings may be fused, as in quinoline orbenzofuran.

“Substituted heterocycle” is heterocycle having one or more side chainsformed from non-interfering substituents.

“Non-interfering substituents” are those groups that yield stablecompounds. Suitable non-interfering substituents or radicals include,but are not limited to, halo, C1-C10 alkyl, C2-C10 alkenyl, C2-C10alkynyl, C1-C10 alkoxy, C7-C12 aralkyl, C7-C12 alkaryl, C3-C10cycloalkyl, C3-C10 cycloalkenyl, phenyl, substituted phenyl, toluoyl,xylenyl, biphenyl, C2-C12 alkoxyalkyl, C7-C12 alkoxyaryl, C7-C12aryloxyalkyl, C6-C12 oxyaryl, C1-C6 alkylsulfinyl, C1-C10 alkylsulfonyl,—(CH₂)_(m)—O—(C1-C10 alkyl) wherein m is from 1 to 8, aryl, substitutedaryl, substituted alkoxy, fluoroalkyl, heterocyclic radical, substitutedheterocyclic radical, nitroalkyl, —NO₂, —CN, —NRC(O)—(C1-C10 alkyl),—C(O)—(C1-C10 alkyl), C2-C10 thioalkyl, —C(O)O—(C1-C10 alkyl), —OH,—SO₂, ═S, —COOH, —NR, carbonyl, —C(O)—(C1-C10 alkyl)-CF₃, —C(O)—CF₃,—C(O)NR₂, —(C1-C10 alkyl)-S—(C6-C12 aryl), —C(O)—(C6-C12 aryl),—(CH₂)_(m)—O—(CH₂)_(m)—O—(C1-C10 alkyl) wherein each m is from 1 to 8,—C(O)NR, —C(S)NR, —SO₂NR, —NRC(O)NR, —NRC(S)NR, salts thereof, and thelike. Each R as used herein is H, alkyl or substituted alkyl, aryl orsubstituted aryl, aralkyl, or alkaryl.

The term “drug”, “biologically active molecule”, “biologically activemoiety” or “biologically active agent”, when used herein means anysubstance which can affect any physical or biochemical properties of abiological organism, including but not limited to, viruses, bacteria,fungi, plants, animals, and humans. In particular, as used herein,biologically active molecules include any substance intended fordiagnosis, cure mitigation, treatment, or prevention of disease inhumans or other animals, or to otherwise enhance physical or mentalwell-being of humans or animals. Examples of biologically activemolecules include, but are not limited to, peptides, proteins, enzymes,small molecule drugs, dyes, nucleosides, oligonucleotides,oligosaccharides, polysaccharides, vaccines, cells, or viruses. Classesof biologically active agents that are suitable for use with theinvention include, but are not limited to, parasiticides, antibiotics,fungicides, anti-viral agents, anti-inflammatory agents, anti-tumoragents, cardiovascular agents, anti-anxiety agents, hormones, growthfactors, steroidal agents, and the like. In some preferred embodiments,the drug or biologically active moiety is a small drug molecule having amolecular weight of less than about 800 Da.

“Lipophilic” or hydrophobic refers to molecules having a greatersolubility in octanol than in water, typically having a much greatersolubility in octanol. Conversely, “hydrophilic” refers to moleculeshaving a greater solubility in water than in octanol.

“Lipid” encompasses oils, fats and fat-like substances that occur inliving organisms and that characteristically are soluble in relativelynonpolar organic solvents (e.g. benzene, chloroform, acetone, ether, andthe like) and sparingly soluble in aqueous solvents. The term includes,but is not limited to, fatty acids, fatty acid esters such astriglycerides, long chain fatty alcohols and waxes, deoxycholate,sphingoids, glycolipids, phospholipids, sphingolipids, and isoprenoids,such as steroids.

“Fatty acid” refers to aliphatic monocarboxylic acids. Fatty acids aretypically predominantly straight chain acids of 4 to about 30 carbonatoms and may be saturated or unsaturated. Branched fatty acids andhydroxy fatty acids are also included in the term.

“Triglyceride” refers to an ester of a fatty acid and glycerol.

“Non-amphipathic”, as used to describe lipids, refers to molecules thatdo not contain both hydrophobic and hydrophilic segments that formbilayers in aqueous solution.

II. Lipophilic Drug Compositions

The present invention provides a method for increasing the lipophilicity(i.e. hydrophobicity) of a drug molecule using two separate approachesthat can be utilized separately or together in a complementary manner.The first approach involves covalent attachment of a lipid molecule to abiologically active drug molecule. The second approach comprisesencapsulating the drug in a lipid composition. By attaching a lipidmolecule to a drug molecule or encapsulating a drug in a lipid, theresulting drug composition becomes more lipophilic, which facilitatestransport of the composition in the lymphatic system as opposed totransport only through blood plasma. The observed ability of thelipid-tailed nitrothiazole to reach and kill parasites in the centralnervous system of horses afflicted with EPM (as described more fullybelow) is suggestive of a lymphatic transport, since most drugs havedifficulty in crossing the blood brain barrier.

The lymphatic pathways begin as lymphatic capillaries, which areclose-ended microscopic tubes forming complex networks. Lymph isessentially tissue fluid that has entered a lymphatic capillary. Thesecapillaries merge with other capillaries to form the lymphatic vesselsand in turn become the lymphatic trunks. The thoracic duct is the majorlymphatic trunk and is similar to the aorta in structure and function.Blood and lymph are the extra-cellular fluids that transport to, andcollect from, tissues and organs. After a fatty meal, at least twothirds of the ingested fat can be recovered in the thoracic duct. Thelymph plus tissue fluid constitutes two thirds of the extra-cellularfluid. This added lymphatic volume is almost three times larger thanblood volume. Bacteria and viruses enter tissue fluids and aretransported as foreign particles through the lymphatic system to thelymph nodes. Foreign particles cannot easily enter the bloodcapillaries, whereas the lymphatic capillaries are easily adapted toreceive them.

Delivery of drug molecules through the lymphatic system provides anumber of important benefits. For example, the effect of acute toxicityof many drugs can be eliminated or greatly reduced. The lipid/drugconjugate or mixture is believed to be more acceptable to the bodybecause it is more “food-like”. In essence, the presence of the lipidmolecule disguises the drug and encourages the body to simply processthe compound as it would any lipid molecule ingested in food. Thus, thelipophilic conjugates or mixtures are processed in a manner thatcontrasts sharply with the manner in which many conventional drugmolecules are processed. Many drugs are immediately recognized asforeign matter and subjected to rejection by the biochemicaldetoxification mechanisms of the patient.

Further, lipophilization of drug molecules increases drug absorption andbioavailability, and slows release of the drug. It is believed that thelipophilic drug compositions of the invention are delivered through thelymphatic tissue fluids to the targeted tissue, rather than passingsolely through the liver. The metabolism of many drugs by liver enzymes,such as cytochrome P450, is well known. Phase 1 biotransformation iscaused by the cytochrome P450 enzymes and a second biotransformationphase, caused by many of the detoxification mechanisms, adds ahydrophilic group, such as glucuronic acid, sulfate or glutathione, andresults in drug inactivation. However, the lipophilic drug compositionsof the invention, such as drug/lipid conjugates droplets, are absorbedand transported through the lymphatic system and are believed to remainactive longer and exhibit slower release profiles. A lipid-like drugwhich enters the lymph can remain in circulation much longer thanconventional drug molecules, due in part to the large size of thelymphatic system as compared to blood volume. The lipophilized drug mayalso be deposited into the adipose tissue, where it is stored andreleased at a slow rate.

In the pharmaceutical industry, there is a general belief thatlipophilicity of a drug must be moderate (i.e. not too high or too low).There is a bell-shaped relationship between the absorption rate and thepartition coefficient, termed log P, in octanol/water. At low P values(log P<−2) (i.e., polar compounds), the drug molecule cannot penetratethe lipid intestinal membrane. Conversely, at high P values (log P>3),the compound becomes so lipid soluble, that the diffusion through themucous layer of the intestinal membrane becomes the rate-limiting stepin the overall absorption process. The conventional view is that a drugmust have a P value of about −1<log P<2 (See Houston, et al., J.Pharmacol. Exp. Ther., 195, 67-92, 1975). Hence, the present inventionof attaching a lipid tail to a drug molecule represents a drasticdeparture from the conventional approach of drug design. Theunconventional nature of this technique is particularly apparent when itis noted that nothing in the crowded field of oxazolidinones suggeststhe type of lipidization of a drug molecule described herein andexemplified in Example 13.

Additionally, attachment of a lipid “tail” to the drug molecule orencapsulation of a drug in a lipid can render the molecule morepalatable to the patient. The usefulness of some orally-administereddrugs is hampered by difficulty in administering the drug at asufficient dosage level due to the unpleasant taste of the drug. Thiscan be particularly problematic in veterinary medicine. By incorporatinga lipid component into the drug composition, the taste of a drug isbetter accepted by the patient and oral administration of the drug canbe improved.

In a preferred aspect of the invention, both approaches are used incomplementary fashion. Thus, in this aspect, a drug molecule iscovalently attached to a lipid molecule and then encapsulated within alipid composition. All of the above-described benefits of druglipidization can be further enhanced by the complementary use of bothlipidization approaches. Further, attaching a lipid molecule to a drugmolecule prior to encapsulation improves the chemical compatibility ofthe drug molecule and the encapsulating lipid components.

A. Covalent Attachment of a Lipid “Tail”

As noted above, in one aspect, the invention provides conjugates of alipid and a biologically active agent. The lipid and drug molecule arecovalently attached through a linkage as illustrated by the generalstructure given below:D-L-LIPID

wherein D is a drug molecule, L is a linkage moiety, and LIPID is aresidue of a lipid. As would be understood, the term “residue” isintended to refer to a portion of a molecule that remains after chemicalreaction with another molecule. When a fatty acid is used as the lipidcomponent, the residue of the lipid component would comprise along-chain alkyl group, such as a C4-C30 alkyl group. It is preferablethat the drug/lipid conjugate form a homogeneous drug product that is awell defined and substantially pure drug entity.

The lipid molecule is preferably a non-amphipathic lipid that is solidat room temperature (25° C.), such as triglycerides or C4-C30 fattyacids. When a fatty acid is used, the fatty acid is preferably a C7-C30fatty acid, more preferably a C10-C30 fatty acid. Thus, it is preferableto use fatty acids having a chain length of at least 7 carbon atoms,more preferably at least about 10 carbon atoms.

In a preferred embodiment, D is a biologically active orpharmacologically active core structure of a known class of activecompounds, thus forming a new drug entity that is efficacious, lesstoxic, and more palatable. By first identifying a biologically activecore structure, the lipidized drug entity will exhibit efficacy, whilealso being as structurally simple as possible for ease of synthesis. Thebiologically active core structure can be identified by analyzingrelated known active compound structures of a given type and selectingthe common structural features shared by all of the active compoundderivatives. In the following three tables, examples of biologicallyactive core structures are illustrated for three classes of drugs:floxins, angiotensin converting enzyme (ACE) inhibitors, andpenicillins. The biologically active core structure for floxins is thefluoroquinolone structure. It is the minimum core drug structure thatconfers the antibiotic activity of floxins (see Table 1). Similarly, forACE inhibitors, the active core structure is the di-peptide ala-prostructure (see Table 2). An example of synthesis of a lipidizedconjugate of an ACE inhibitor is discussed in Example 14. Forpenicillins, the B lactam and thioazolidine rings form the biologicallyactive core structure (see Table 3).

TABLE 1 Floxins (core structure = fluoroquinolones) Ciprofloxicin

Fleroxacin

Ofloxacin

Enrofloxicin

TABLE 2 ACE Inhibitors (core structure = dipeptide ala-pro) Captopril

Enalapril

Lisinopril

Imidapril

TABLE 3 Penicillins (core structure = B-lactam plus thioazolidine rings)Amoxicillin

Ampicillin

Propicillin

As would be understood in the art, a drug molecule can be covalentlyattached to a lipid by reacting a terminal reactive group on the lipidmolecule with a reactive group on the drug molecule. For example, withregard to the synthesis of the new drug, 2-lauramide-5-nitrothiazole,which is described in greater detail below, the carboxy function oflauric acid is reacted with the amino group of 2-amino-5-nitrothiazolein a condensation reaction to form an amide linkage between the drugmolecule and the lipid molecule.

If necessary, either the drug molecule or the lipid component, or both,may be chemically modified to form the reactive groups necessary forconjugation. For instance, lauric acid or other fatty acids can be“activated” to form a reactive species that will react readily with anamino group on a drug molecule to form an amide linker. Examples of suchactivated derivatives include fatty acid-acyl-halides and active estersof fatty acids, such as N-hydroxysuccimidyl esters. Lipids can also beactivated with carbodiimadzole or carbodiimide. Conversely, asubstituent of the drug molecule, such as a carboxyl group, can beactivated and reacted with a long chain alkylamine, such as a C4-C30alkylamine. In yet another embodiment, a bifunctional linker, such asbromoacetobromide, can be used to bromoacetylate an alkylamine, which isthen reacted with an amino functionality on a drug molecule to form aconjugate having the general structure LIPID-NH—CH₂—CO—NH-DRUG. In allthree examples, a peptide linkage is generated that can be cleavedenzymatically by a non-specific endopeptidase.

There are numerous examples of reactive functional groups that can beformed on a lipid molecule or drug molecule for reaction with othermolecules. Exemplary functional groups include hydroxyl, active esters(e.g. N-hydroxysuccinimidyl, 1-benzotriazolyl, p-nitrophenyl, orimidazolyl esters), active carbonates (e.g. N-hydroxysuccinimidyl,1-benzotriazolyl, p-nitrophenyl, or imidazolyl carbonate), acetal,aldehyde, aldehyde hydrates, alkyl or aryl sulfonate, halide, disulfidederivatives such as o-pyridyl disulfidyl, alkenyl, acrylate,methacrylate, acrylamide, active sulfone, amine, hydrazide, thiol,carboxylic acid, isocyanate, isothiocyanate, maleimide, vinylsulfone,dithiopyridine, vinylpyridine, iodoacetamide, epoxide, glyoxals, diones,mesylates, tosylates, or tresylate.

The linkage, L, is any type of linkage resulting from the reaction of afunctional group on the lipid and a functional group on the drugmolecule, or resulting from reaction of a bifunctional linker with adrug molecule and an alkylamine. Examples of suitable linkages includecarboxylic acid esters, phosphoesters, thioesters, ethers, thioethers,imides, amides, sulfonamides, phosphonamides, disulfides, andcarbamides. The linkage, L, formed between the drug molecule and thelipid molecule is preferably a hydrolytically stable linkage, such asethers, thioethers, imides, amides, sulfonamides, phosphonamides,disulfides, and carbamides. The linkage moiety should also beenzymatically cleavable, such as a linkage cleavable by esterase,peptidase, hydrolase and the like. In this manner, the parent drugcompound will be released from the lipid tail by interaction with one ormore enzymes. Amide and imide linkages are particularly preferredenzymatically cleavable, hydrolytically stable linkages. In someembodiments, hydrolytically degradable linkages, such as certain esters,can also be used.

B. Encapsulation of Drug Within Lipid Component

In another aspect of the invention, drug molecules or drugmolecule/lipid conjugates are encapsulated by an inert matrix of one ormore lipid components to enhance lipidization of the drug molecule andfacilitate lymphatic transport. By encapsulating a drug in a protectivehydrophobic environment, product stability is also enhanced. Theencapsulating lipid is preferably non-amphipathic, meaning the lipidcomposition used for encapsulation is substantially free ofphospholipids, glycolipids or other amphipathic lipids that formbilayers in solution. The encapsulated drug product of the inventionpreferably comprises a single phase (e.g., solid or liquid). Preferably,the encapsulated drug product is a dry solid, meaning a solidsubstantially free of water or other solvents. In one embodiment, theencapsulating lipid composition comprises lipids that are solid at 25°C., such as triglycerides, C4-C30 fatty acids or mixtures thereof. Theterm “encapsulation” means that the lipid composition is in contactwith, and physically surrounds and entraps, a substantial portion of thedrug combined therewith such that a substantial portion of the drug isno longer physically exposed to the surrounding environment.

When a lipid/drug conjugate is encapsulated, the encapsulating lipid canbe isologous (i.e., the lipid used to form the conjugate is identical inchain length to the lipid used in encapsulation), homologous (i.e., thelipids are similar but differ in chain length), or heterologous (i.e.,the conjugating lipid is substantially different from the encapsulatinglipid, such as one is unsaturated and the other is saturated or one is aphospholipid and the other is a fatty acid). For example, if a C12 fattyacid is attached to a biologically active agent, then an isologousencapsulating lipid composition would comprise, for example, C12 fattyacids and/or triglycerides comprising C12 alkyl chains. A homologousencapsulating lipid composition would comprise lipid components havingalkyl chain lengths, for example, within about 5 carbons atoms of thelength of the lipid tail attached to the biologically active agent,preferably within about 3 carbon atoms. It is generally preferable toattach the drug to a lipid that is chemically compatible andstructurally similar to the encapsulating lipid components, such thatthe lipid tail and the encapsulating lipid are isologous or homologouslipid compositions.

The encapsulation method of the invention involves blending of the lipidcomponent with the drug molecule and is both simple and low cost. Therationale behind this approach is grounded in basic biochemicalknowledge of fat metabolism. In higher mammals, including humans, themetabolism transport and deposition of fat is a known biochemicaltransformation. Neutral fats or triglycerides are composed of three longfatty acid chains esterified to the trihydric alcohol of glycerol.Ingested fats are emulsified in the small intestine by bile salts tobecome micelles or oil droplets that are absorbed away from theintestine lumen by lymphatic capillaries. The relatively large absorbedfat micelles known as chylomicrons pass from the intestine through thelymph into the blood. By encapsulating the drug molecule in a lipidcomposition, the invention mimics the fat micelles in order to enhancethe drug absorption from the intestine milieu.

In a preferred embodiment, drug crystals are emulsified with fatty acidsand then encapsulated in triglycerides. A preferred triglyceridecomposition is Sterotex® NF, a fully hydrogenated cottonseed oilavailable from Albitec Corp. of Janesville, Wis. Sterotex® NF comprisesglycerin esters of C14-C22 fatty acids. In pharmaceutical manufacturing,it is a well-known excipient, usually added as a lubricant during thegranulation process in tableting. However, in this application, Sterotexis used as a component of an enteric drug delivery formulation.

Although encapsulation with Sterotex® alone has proven to be effective(see Examples 1-3) for drug delivery through the lymphatic system,improved drug delivery is seen when a fatty acid, such as palmitic acid,is incorporated into the process. Example 4 provides a general processfor encapsulating a drug in a triglyceride/fatty acid complex. Ingeneral terms, the process comprises high shear blending or mixing ofthe drug or drug/lipid conjugate with one or more fatty acids, such asC4-C30 fatty acids, in the presence of a solvent, to form an emulsion.While continuing to subject the emulsion to high shear blending ormixing, a triglyceride or mixture of triglycerides, such as Sterotex®,is added to the emulsion and mixed therewith using high shear blending.The mixture is then cooled to form a solid composition and dried. It isimportant to mix the drug with the lipid components with sufficientmixing intensity to form an emulsion. The high shear mixing or blendingcan be accomplished using high speed or high pressure mixing equipmentor by sonification. Examples of suitable mixing apparatus known in theart include Microfluidizer® processors, blenders, sonicators,homogenizers, as well as other mixing apparatus. The mixing energygenerated by the high shear blending results in emulsion formation suchthat the encapsulating lipids and the encapsulated drug or drug/lipidconjugate coalesce into an ordered, layered structure, as evidenced bythe freeze-fracture EM photographs referred to in Example 7.

There are a number of reasons for incorporating fatty acids into thedrug/lipid complex. First, fatty acids in fat droplets control fatmetabolism by pancreatic lipase. In the normal course of fat metabolism,triglycerides are degraded to diglycerides+fatty acids and diglyceridesare degraded to monoglycerides+ more fatty acids and monoglycerides aredegraded to fatty acids and glycerol. In the presence of free fattyacids, the lipases are less active towards the triglycerides. If thelipase remain highly active, the crystalline drug can be uncoated byconverting triglyceride to glycerol and fatty acids. Fatty acids act asan end-product inhibition of the enzyme lipase and thereby prevent theremoval of the lipid coating of the encapsulated drug crystals. Second,some polar drugs are difficult to emulsify with fat, whereas fatty acidspossessing a carboxylic moiety can better interact with the drug.Lastly, the 85% bound drug found in Example 2 suggests that the complexwith Sterotex® could be further improved.

The solvents and fatty acids used in emulsifying a given drug can bemodified to accommodate the chemistry of the drug. For example, ethanolor water can be substituted for methanol used in Example 4. Palmiticacid, exemplified in Example 4, is a C-16 carbon chain fatty acid.Substitutions with shorter or longer carbon chains and even deoxycholicacid have been found to be suitable. Preferably, the fatty acid is aC4-C30 fatty acid. In some embodiments, it is preferred to use a C7-C30fatty acid, more preferably a C10-C30 fatty acid. Thus, it is preferableto use fatty acids having a chain length of at least 7 carbon atoms,more preferably at least about 10 carbon atoms.

Preferably, the weight ratio of the encapsulating lipid component to thedrug in the final composition is about 4:1 to about 0.25:1, preferablyabout 2:1 to about 0.5:1, more preferably about 1:1. If a combination oftriglyceride and fatty acid is used as the encapsulating lipid, theweight ratio of triglyceride to fatty acid is preferably about 4:1 toabout 1:4, more preferably about 3:1 to about 1:3, most preferably about2:1 to about 1:2 or about 1:1.

Prior to degradation in vivo, it is preferable for no more than about 50weight percent, more preferably no more than about 30 weight percent,and most preferably no more than 10 weight percent, of the bound drug tobe physically exposed within the composition. By physically exposed ismeant that a portion of the drug molecule is exposed to the environmentexternal to the encapsulating lipid composition.

The most advantageous use of the encapsulated formulation of theinvention is in oral medication. Virtually all enteric medications havean unpleasant taste and are often bitter. Sterotex® is odorless andtasteless and therefore can be added to food and is acceptable torecipients.

The encapsulation process of the invention is simple and economical(both Sterotex® and palmitic acid are less than $0.02/g). Theencapsulated drug complex is stable and yet biologically available. Itis palatable to humans and animals and drug absorption through thegastrointestinal tract is enhanced. It guards against acute drugreleases and avoids the toxicity of many potent cytotoxic drugs.

C. The Biologically Active Agent

The biologically active moiety or drug may be any biologically activecompound that would benefit from lymphatic delivery and benefit from theadvantages of lipophilization described above, such as increasedcirculation time, reduced toxicity, etc. Virtually any biologicallyactive compound would benefit from the lipid encapsulation/attachmentmethodology described herein. In particular, the following classes ofdrugs would-benefit from the present invention: cephalosporins,peptides, ACE inhibitors, antibiotics, anticancer, anti-depressant,antihistamine, anti-psychotic, cardiovascular, gastrointestinal,anti-hypertensive, diuretic, amino acid, nucleotide, nucleoside,vaccine, polysaccharide, protein, tranquilizers, narcotics,anti-arthritic, anti-viral, anti-asthmatic, anti-allergy, and the like.

The drug may be utilized per se or in the form of a pharmaceuticallyacceptable salt. If used, a salt of the drug compound should be bothpharmacologically and pharmaceutically acceptable, butnon-pharmaceutically acceptable salts may conveniently be used toprepare the free active compound or pharmaceutically acceptable saltsthereof and are not excluded from the scope of this invention. Suchpharmacologically and pharmaceutically acceptable salts can be preparedby reaction of the drug with an organic or inorganic acid, usingstandard methods detailed in the literature. Examples of useful saltsinclude, but are not limited to, those prepared from the followingacids: hydrochloric, hydrobromic, sulfuric, nitric, phosphoric, maleic,acetic, salicyclic, p-toluenesulfonic, tartaric, citric,methanesulphonic, formic, malonic, succinic, naphthalene-2-sulphonic andbenzenesulphonic, and the like. Also, pharmaceutically acceptable saltscan be prepared as alkaline metal or alkaline earth salts, such assodium, potassium, or calcium salts of a carboxylic acid group.

III. Exemplary Lipophilic Drug Compositions

A. Lipophilic Nitrothiazole Compositions

Equine protozoal myeloencephalitis (EPM) is caused by the intracellularprotozoal organism Sarcocystis neuron a infecting the CNS. In clinicallyaffected horses, the protozoans infect neurons and induce aninflammatory response. Clinical signs of neurological disease mostcommonly result in asymmetric coordination (ataxia) weakness, and/ormuscle atrophy. The infection progressively worsens and the untreatedanimals eventually collapse and die. Up to 60% of the horses in someareas of the country, including the Southeast, have been exposed to S.neurona. It is estimated that 10% of exposed horses exhibit neurologicalsigns of EPM.

Nitazoxanide (2 acetolyoxy-N-5 nitro-2-thiazolyl otherwise known as NTZ)is a pharmaceutical composition highly effective against a wide varietyof parasites, bacteria and viruses in both animals and humans. In thetreatment of EPM, it has been shown to be effective against thecausative parasite S. neurona. The advantage of this pharmaceuticalcomposition is that it is a wide spectrum antibiotic and its mode ofaction is cidal rather than static. The disadvantage of the drug is thatin the free form it is relatively toxic. It is also not palatable andcauses anorexia, depression and diathermia or loose stool in horses. Inhumans, NTZ has been known to cause gastrointestinal upset in thetreatment of cryptosporidial diarrhea. The drug also has some safetyissues principally due to nitrothiazole. The very nature of itsconstruct along with the aspirin conjugation further exacerbates thegastrointestinal intolerance and damage. Salicylates cause epithelialcell damage and widen both the intracellular junction spaces and thepores of the epithelial cell (see Kingham et. al. Gut 17:354-359(1976).The drug, like aspirin, is unstable because it is susceptible tomoisture degradation from the ester to the deacetylated form. Instability studies, the bulk drug progressively degrades. In addition,the sulfur also oxidizes to sulfone and then to sulfoxide as can bevisualized by UV scanning from UV max of 350 nm. It is red-shifted to354 nm (sulfone) and then 358 nm (sulfoxide). When the drug is heated tomore than 50° C. the oxidation is most pronounced. The bulk drug has anexpiry of two years. A number of patents discuss 5-nitrothiazolederivatives, including U.S. Pat. Nos. 3,950,351; 4,315,018; 5,856,348;5,859,038; 5,886,013; 5,935,591; 5,965,590; 5,968,961; 6,020,353; and6,117,894, all of which are incorporated herein by reference.

The present invention provides a safe and efficacious pharmaceuticalcomposition comprising nitrothiazole for the treatment of opportunisticmicrobes in both humans and animals. It overcomes many safety issues andespecially the stability problem of nitazoxanide. The new drug moleculecomprises a lipid molecule, such as a fatty acid, covalently attached toa substituted or unsubstituted 5-nitrothiazole compound or derivativethereof, including 2-benzamido-5-nitrothiazole compounds, wherein thearyl ring of the benzamido group may be substituted or unsubstituted(preferred substituents including hydrogen, acyloxy, such as acetoxy orpropionoxy, halogen, and alkoxy). Any of the 5-nitro thiazole compoundsdisclosed in the patents referenced above can be used in the presentinvention. The lipid molecule can be attached to any atom of any ringstructure in the molecule (e.g., the thiazole ring or the aryl ring ofthe benzamido group), either directly or through a linkage, such as anamide linkage.

A preferred lipid conjugate of a 5-nitrothiazole compound is shown asFormula I below:

wherein L is a linkage, such as —NH—C(O)—, R is hydrogen, alkyl,substituted alkyl, aryl, substituted aryl, heteroaryl, substitutedheteroaryl, heterocyclic, or substituted heterocyclic, and LIPID is aresidue of a lipid, such as a C4-C30 fatty acid. A specific embodimentof a compound of Formula I, 2-lauramide-5-nitrothiazole, is alsoreferred to herein as BA 3540. BA 3540 is chemically synthesized bycondensing the carboxyl function of lauric acid to the amino group of2-amino-5-nitrothiazole (see Example 8). As known to the skilledartisan, activating agents that may be used to form the amide linkageinclude many activated intermediates of lauryl-acyl-halides,lauryl-active esters such as lauryl-n-hydroxysuccimide ester and also byactivation with carbodiimadzole and carbodiimide.

The therapeutic efficacy of the new drug 2-lauramide-5-nitrothiazole isremarkable. The new drug construct must find its way from the intestineto the CNS and it has to possess the cidal activity of NTZ in order toeradicate the parasite. The mechanism of action of the new drug iscurrently unknown. However, natural multiple thiazole rings peptideantibiotic produced by streptomycetes such as thiostrepton andmicorococcin shed light on this issue. The mechanism of action of theantibiotic is due to the binding of the thiazole ring, which inhibitstranslation and ribosomal GTPase activity. This binding is to a limitedand conserved region in the large subunit rRNA found in eubacteria and(plastid) organelles and not to the corresponding region in eukaryotes.Effective treatment of crytosporadium, plasmodium, and toxoplasma bynitrothiazole may also be due to inhibition of plastid-like organellecontained in these parasites. Although not bound by any particulartheory, it is reasonable to assume that the new drug2-lauramide-5-nitrothiazole also functions in the same manner. Thisdiscovery in view of the present disclosure has far reachingimplications.

NTZ has been proposed for the treatment of a wide variety of parasites,fungi, bacteria and viruses. The new drug 2-lauramide-5-nitrothiazole isequally as effective as NTZ in the treatment of EPM. Thus, it stands toreason that the new drug can be as effective against the same class ofopportunistic parasites, fungi, bacteria and viruses. In particular, thenitrothiazole/lipid conjugate of the invention is useful as a treatmentof parasitic, bacterial, viral or fungal infection, including infectionby nematodes, cestodes, trematodes, and gram + or gram − bacteria, byadministering a therapeutically effective amount of the conjugate to theinfected mammal (See Examples 9-12). For instance, thenitrothiazole/lipid conjugates of the invention have proven effectiveagainst protozoan parasites, such as parasites that cause EPM andcoccidiosis, as well as against viruses.

The metabolism of nitazoxanide has been shown to involve deacetylationto tyazoxinide. In view of the present disclosure, the active metabolitecannot be due solely to tyazoxinide. The commonality between the twoactive drugs is the parent compound 2-amino-5-nitrothiazole. In-vivo, anonspecific endopeptidase can cleave both molecules to2-amino-5-nitrothioazole. This may offer a hint to the identity of theprimary metabolite for both drugs.

In another aspect, the present invention provides nitrothiazole, such asthe nitrothiazole derivatives described above (whether conjugated to alipid or in free form), encapsulated by a lipid composition, such astriglycerides, fatty acids or mixtures thereof, using the methodologydescribed above (see Examples 3 and 6). As noted above and in theappended examples, encapsulating NTZ or other nitrothiazole derivativesin a lipid composition can improve efficacy and bioavailability andreduce toxicity.

B. Lipophilic Ivermectin Compositions

As noted in Examples 5 and 6, ivermectin was encapsulated within a lipidcomposition and shown to be well tolerated by the patient and effective.The encapsulation method taught herein can also be used with relatedabamectin, avermectin, moxidectin, and milbemycin compounds.

C. Lipophilic Oxazolidinone Compositions

As noted in Example 13, the lipid attachment and/or encapsulationmethodology of the present invention can also be used with2-oxazolidinones. As shown in the appended example, a 2-oxazolidinonederivative can be covalently attached to a lipid molecule, such as aC4-C30 fatty acid to form a lipophilic derivative. Oxazolidinones areuseful as antibacterial agents. Numerous 2-oxazolidinone derivatives aredescribed in U.S. Pat. Nos. 3,931,213; 4,186,129; 5,643,907; 5,565,571;5,668,286; 5,688,792; 5,700,799; 5,719,154; 6,166,056; 6,288,238; and6,337,329, as well as EP 0 316 594 A1, all of which are incorporated bereference herein. Any 2-oxazolidinone compound can be encapsulated witha lipid composition and/or covalently attached to a lipid molecule,either directly or through a linkage moiety. For example, any of theoxazolidinones described in the above references could be used in thepresent invention. Preferably, the 2-oxazolidinone derivatives aresubstituted at one or more of the atoms of the ring structure, withpreferred ring substituents including hydrogen, aryl, substituted aryl,alkyl, substituted alkyl including alkoxy, halogen, CF₃, acyl, amino,substituted amino, and RS(O)_(n)—, wherein n is 1-2 and R is alkyl orsubstituted alkyl. A lipid molecule can be attached to any availableatom of the oxazolidinone ring or any atom of any aryl ring attached tothe oxazolidinone ring.

In one preferred embodiment, the lipid/oxazolidinone conjugate has theFormula II below:

wherein L is a linkage, such as an imide linkage, each R isindependently hydrogen, alkyl, substituted alkyl, aryl, substitutedaryl, heteroaryl, substituted heteroaryl, heterocyclic, or substitutedheterocyclic, and LIPID is a residue of a lipid, such as a C4-C30 fattyacid.

D. Lipophilic Nitroimidazole Compositions

As shown in Example 14, the present invention is also useful in forminglipophilic 5-nitroimidazole compositions. For example, lipid moleculescan be covalently attached, either directly or through a linkage, to anyavailable atom in a 5-nitroimidazole ring. In one embodiment, thelipid/drug conjugate as the structure shown below as Formula III:

wherein L is a linkage, such as imide, each R is independently hydrogen,alkyl, substituted alkyl, aryl, substituted aryl, heteroaryl,substituted heteroaryl, heterocyclic, or substituted heterocyclic, andLIPID is a residue of a lipid, such as a C4-C30 fatty acid.IV. Pharmaceutical Composition Comprising the Lipophilic DrugComposition

In another aspect, the invention provides pharmaceutical formulations orcompositions, both for veterinary and for human medical use, comprisinga lipophilic drug composition as described above comprising a drugcovalently attached to, and/or encapsulated within, a lipid.

The pharmaceutical formulation may include one or more pharmaceuticallyacceptable carriers, and optionally any other therapeutic ingredients,stabilizers, or the like. The carrier(s) must be pharmaceuticallyacceptable in the sense of being compatible with the other ingredientsof the formulation and not unduly deleterious to the recipient thereofThe compositions of the invention may also include polymericexcipients/additives or carriers, e.g., polyvinylpyrrolidones,derivatized celluloses such as hydroxymethylcellulose,hydroxyethylcellulose, and hydroxypropylmethylcellulose, Ficolls (apolymeric sugar), hydroxyethylstarch (HES), dextrates (e.g.,cyclodextrins, such as 2-hydroxypropyl-β-cyclodextrin andsulfobutylether-β-cyclodextrin), polyethylene glycols, and pectin. Thecompositions may further include diluents, buffers, binders,disintegrants, thickeners, lubricants, preservatives (includingantioxidants), flavoring agents, taste-masking agents, inorganic salts(e.g., sodium chloride), antimicrobial agents (e.g., benzalkoniumchloride), sweeteners, antistatic agents, surfactants (e.g.,polysorbates such as “TWEEN 20” and “TWEEN 80”, and pluronics such asF68 and F88, available from BASF), sorbitan esters, lipids (e.g.,phospholipids such as lecithin and other phosphatidylcholines,phosphatidylethanolamines, fatty acids and fatty esters, steroids (e.g.,cholesterol)), and chelating agents (e.g., EDTA, zinc and other suchsuitable cations). Other pharmaceutical excipients and/or additivessuitable for-use in the compositions according to the invention arelisted in “Remington: The Science & Practice of Pharmacy”, 19^(th) ed.,Williams & Williams, (1995), and in the “Physician's Desk Reference”,52^(nd) ed., Medical Economics, Montvale, N.J. (1998), and in “Handbookof Pharmaceutical Excipients”, Third Ed., Ed. A. H. Kibbe,Pharmaceutical Press, 2000.

The lipophilic drug compositions of the invention may be formulated incompositions including those suitable for oral, buccal, rectal, topical,nasal, ophthalmic, or parenteral (including intraperitoneal,intravenous, subcutaneous, or intramuscular injection) administration.The lipophilic drug compositions may also be used in formulationssuitable for inhalation. Oral administration is a particularlyadvantageous route of administration for the present invention in lightof the increased intestinal absorption and palatability characteristicsof the drug compositions of the present invention, as described above.The compositions may conveniently be presented in unit dosage form andmay be prepared by any of the methods well known in the art of pharmacy.All methods include the step of bringing the drug composition intoassociation with a carrier that constitutes one or more accessoryingredients. In general, the pharmaceutical compositions are prepared bybringing the drug compositions of the invention into association with aliquid carrier to form a solution or a suspension, or alternatively,bringing the drug composition into association with formulationcomponents suitable for forming a solid, optionally a particulateproduct, and then, if warranted, shaping the product into a desireddelivery form. Solid formulations of the invention, when particulate,will typically comprise particles with sizes ranging from about 1nanometer to about 500 microns. In general, for solid formulationsintended for intravenous administration, particles will typically rangefrom about 1 nm to about 10 microns in diameter.

The amount of the biologically active agent or drug in the formulationwill vary depending upon the specific drug employed, its molecularweight, and other factors such as dosage form, target patientpopulation, and other considerations, and will generally be readilydetermined by one skilled in the art. The amount of biologically activeagent in the composition will be that amount necessary to deliver atherapeutically effective amount of the drug to a patient in needthereof to achieve at least one of the therapeutic effects associatedwith the drug. In practice, this will vary widely depending upon theparticular drug, its activity, the severity of the condition to betreated, the patient population, the stability of the formulation, andthe like. Compositions will generally contain anywhere from about 1% byweight to about 80% by weight drug, typically from about 10% to about60% by weight drug, and more typically from about 25% to about 50% byweight drug, and will also depend upon the relative amounts ofexcipients/additives contained in the composition. More specifically,the composition will typically contain at least about one of thefollowing percentages of the drug: 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%,9%, 10%, 12%, 14%, 16%, 18%, 20%, 25%, 30%, 35%, 40%, 45% or more byweight.

V. Method of Using the Lipophilic Drug Compositions

As noted above, the lipophilic drug compositions of the invention can beused to improve efficacy, bioavailability, and absorption, as well asreduce toxicity, of a variety of drug molecules. As a result, thecompositions of the invention may be used as drug delivery vehicles byentrapping a drug within, or attaching a drug to, a lipid component,such as a triglyceride or fatty acid, and administering atherapeutically effective amount of the resulting composition to amammal.

The drug compositions of the invention can be used as drug deliveryvehicles for any condition responsive to the attached or entrapped drugmolecule. Thus, the drug compositions of the invention can be used inpharmaceutical formulations usefuil for treating any conditionresponsive to the drug molecule in mammals, including humans. The methodof treatment comprises administering to the mammal a therapeuticallyeffective amount of a composition or formulation containing thelipophilic drug composition described above. The therapeuticallyeffective dosage amount of any specific formulation will vary somewhatfrom drug to drug, patient to patient, and will depend upon factors suchas the condition of the patient and the route of delivery. As a generalproposition, a dosage from about 0.5 to about 100 mg/kg body weight willhave therapeutic efficacy. For example, in certain embodiments, thedosage will be about 10, about 20, about 50, about 75 or about 100mg/kg. When administered conjointly with other pharmaceutically activeagents, even less of the drug composition may be therapeuticallyeffective.

The drug composition may be administered once or several times a day.The duration of the treatment may be once per day for a period of fromtwo to three weeks and may continue for a period of months or evenyears. The daily dose can be administered either by a single dose in theform of an individual dosage unit or several smaller dosage units or bymultiple administration of subdivided dosages at certain intervals.Possible routes of delivery include buccally, subcutaneously,transdermally, intramuscularly, intravenously, orally, or by inhalation.

VI. Experimantal

The following examples are given to illustrate the invention, but shouldnot be considered in limitation of the invention.

EXAMPLE 1 Encapsulation of Drug in Triglyceride

A general process that can be adapted for direct encapsulation of drugcrystals in a triglyceride or mixture thereof, such as Sterotex®, isdescribed in U.S. Pat. No. 6,153,119, which is incorporated herein byreference.

As an example of such a process, 10 g Sterotex® is weighed into a 100 mLscrew-cap bottle whereby 30 mL of isooctane or hexane is added andheated to dissolve slowly. The solubilized Sterotex® is maintained at50° C. An equal weight of drug, 10 g is added to the solubilizedSterotex® and the mixture is shaken vigorously for 5-10 minutes. Theresultant mixture is quick cooled in an ice bath while shaking and/orswirling. The cooling mixture will become molten and then slowlysolidify. Transfer to a container and dry by pulling vacuum overnight toremove all volatile solvents. The yield is 20 g of 1:1 Sterotex®/drugcomplex which is usually a white product that can be broken-up into afine powder. Virtually all pharmaceutical drugs can be emulsified andtrapped in this manner.

EXAMPLE 2 Encapsulation of Aspirin in Triglyceride

Aspirin possesses an active ester function and is susceptible toalkaline degradation. In this example, aspirin is encapsulated inSterotex® using the method described in Example 1. In aspirin, thedeacetylated species is salicylic acid, which has a characteristicabsorbency at 296 nm. The comparison of drug stability ofSterotex®/aspirin vs. aspirin was made in 0.1 M NaCO₃ (10 pH) and thekinetics of degradation monitored by UV spectrophotometry. In FIG. 1,the appearance of salicylic acid is compared between aspirinencapsulated in Sterotex® and free aspirin. Aspirin slowly dissolves andis hydrolyzed to salicylic acid in a basic solution of 0.1 M NaCO₃. At27 hours, it is roughly 38% hydrolyzed. By contrast, aspirinencapsulated in Sterotex® is quite stable even at 27 hours and is onlyless than 2% degraded. This example illustrates the increase in drugstability provided by encapsulation in a lipid component.

EXAMPLE 3 Encapsulation of Acetylbenzamide Nitrothiazole in Triglyceride

Acetylbenzamide nitrothiazole, otherwise known as NTZ, is an antibioticdrug useful as a treatment for protozoan parasites. Acetylbenzamidenitrothiazole also possesses an active ester function that issusceptible to alkaline degradation to form hydroxybenzamidenitrothiazole with a characteristic absorbency at 360 nm. In water, theparent drug is sparingly soluble and the solution is colorless. Uponstanding overnight, the parent drug is converted to the deacetylatedcounterpart and an intense yellow solution is formed. Acetylbenzamidenitrothiazole encapsulated by Sterotex® as described in Example 1 ishydrophobic and remains afloat on the water surface. A light yellowsolution results after many hours at room temperature.

A reasonable estimate of bound versus free drug by UV spectrometrysuggests that about 85% of the drug crystals are totally buried inSterotex®. By increasing the ratio of Sterotex® to drug, this exposeddrug percentage does not improve. This higher than expected percentageof free drug suggests that when Sterotex®/nitrothiazole complex isbroken-up into fine powder, some drug crystals may be partially exposedand become available to the aqueous milieu. The kinetic of degradationof acetylbenzamide nitrothiazole in 0.1 M NaCO₃ is similar to theaspirin curve of FIG. 1. For comparison, the encapsulated drug at 3hours showed an optical density of 0.1, while the free drug has anoptical density of 1.9. This example also illustrates the stabilizingeffect of lipid encapsulation.

Sterotex® encapsulates the drug in a hydrophobic environment and it isof utmost importance to show that the drug is bioavailable. The in-vitrobioavailability of acetylbenzamide nitrothiazole in the bound complexwas further examined by dissolution testing. The complex versus freenitrothiazole was compared in a Distek® Dissolution Apparatus at 37° C.,employing the paddle method (Apparatus I) in 0.1M HCl both with andwithout a detergent (1% Triton X100). The dissolution of free andSterotex®-complexed drug (at a ratio of Sterotex®: Drug of: 0.5, 2.0 and2.5) was first compared at 100 rpm for 120 minutes. Under thiscondition, all samples show about the same extent of drug release and atthe end of dissolution the maximum O.D. was 0.2. When 1% Triton X100 wasadded to the dissolution media, the drug dissolution was more rapid,although still incomplete. The rate profile of dissolution shows thatthe Sterotex®/nitrothiazole is about the same as that of the free drug(see FIG. 2).

EXAMPLE 4 Encapsulation of Drug within Fatty Acid and Triglyceride

In the process described below, the drug is first emulsified with highshear blending of a free fatty acid, such as palmitic acid, in asolvent, such as a mixture of methanol and isooctane. The complex formedis coated a second time with Sterotex®. To 125 gm drug, 135 ml ofmethanol is added in a variable speed Waring blender. The blender isoperated 2-3 times at intermediate speed and stopped at intervals toprevent overheating. The total grinding time is 10 minutes at top speed.At this stage, 25 g of palmitic acid (C-16) and 50 ml of isooctane areadded. The blender is turned on for ten minutes at intermediate speed.The formation of an emulsion is carefully monitored and more isooctanecan be added if the paste is too thick. The blender is then operated attop speed for 30 minutes and again taking care not to allow thetemperature to rise above 55° C. When the emulsion thickens, 100 g ofmelted Sterotex® at about 60° C. is slowly added to the blender while atlow speed. Repeat the steps of emulsion grinding at top speed as before.Then the blender is quick cooled in an ice bath. The solidifiedSterotex®/palmitic/drug is dried overnight in a vacuum chamber. Thefinal ratio of Sterotex®: palmitic acid is 4:1, and their combinedweight ratio to drug remains at ˜1:1.

EXAMPLE 5 In-vivo Testing of Sterotex®/Ivermectin andSterotex®V/Palmitic/Ivermectin

Two oral Sterotex© formulations of the anathematic drug, Ivermectin, wasadministered to two horses. Conventional formulations consist of eitherIvermectin in a paste or in an oil drench that has to be administered byforce-feeding. On a monthly basis, horses need to be de-wormed withIvermectin treatment. The Ivermectin was encapsulated by eitherformulation, Sterotex®/vermectin and Sterotex®/palmitic/Ivermectin, asdescribed above in Examples 1 and 4. The palatability test was performedby adding 1:1 Sterotex®/drug and Sterotex®: palmitic/drug to a handfulof sweet feed consisting of molasses and alfalfa. The time of ingestionwas recorded and the horses found either formulation acceptable andconsumed both in about the same amount of time as the control sweetfeed. The voluntary oral uptake of the drug complex in this and otherexperiments by horses demonstrate its acceptability as an entericformulation.

The in-vivo bioavailability was assessed by studying the pharmacokineticof the drug in individual horses that are treated with either Ivermectinformulation. Blood samples were taken at various times after dosing andplasma were prepared and kept frozen until all samples had beencollected. In FIG. 3, the pharmacokinetic profile is the result of HPLC(high pressure liquid chromatography) analysis by fluorescence ofIvermectin recovered in the blood samples. As shown, the encapsulatedformulations exhibited a normal pharmacokinetic profile after a singledose.

EXAMPLE 6 Efficacy of Sterotex®/Ivermectin and Sterotex®/AcetylbenzamideNitrothiazole in Horses

The efficacy of the Sterotex/Ivermectin formulation was assessed byparasite egg count present in the horse feces before and after drugtreatment. The egg count before treatment was 350 eggs/L and aftertreatment it was zero.

The conventional acetylbenzamide nitrothiazole paste is used as atreatment for horses for 6 days at 25 mg/Kg and then at 50 mg/kg bodyweight daily for a total of 28 treatments. In clinical trials, anencapsulated NTZ formulation (formulated as in Example 4 with bothSterotex® and palmitic acid) was used to treat 4 horses with clinicalsigns of Equine Protozoal Myeloencephalitis (EPM) at half dose (i.e. 25mg/Kg) and one horse was treated at one-third dose (i.e., 16.7 mg/kg).The horses infected with neurological protozoan parasites recoveredcompletely after 28 treatments. The treatment with conventional NTZ inother studies remained at 80% efficacy.

The efficacy results indicate that the drug absorption in thegastrointestinal tract is vastly improved by the Sterotex/palmiticencapsulation formulation. It may also be due to the fact that some ofthe drug may be transported through the lymphatic system and be moreeffectively delivered through the tissue/body fluids to the targetedneurological organs.

EXAMPLE 7 Freeze Fracture Electron Microscopy Study of the EncapsulatedComplex of Sterotex®/Palmitic/Nitrothiazole

For freeze-fracture electron microscopy, the samples were quenched usinga sandwich technique and liquid nitrogen-cooled propane. The fracturedplanes were shadowed with platinum for 30 seconds at an angle of 25-35degrees and with carbon for 35 seconds. The replicas were cleaned withconcentrated fuming HNO₃ for 24-36 hours. The electron micrographs ofFIG. 4 taken at a final magnification of 27,390 show extended areas oflayered structures. Presumably, these are ordered lipid layers becausein cross-fraction regions, steps of about 4-6 nm are observable. Somestructural features that resemble H_(II) lipid phase and the beginningof lipid-tubule-growth are also discernable.

FIG. 5 was taken at 8.3K magnifications. In the final magnification, 1μm=3.2 cm. In the electron photograph, areas labeled C=Crystal of drug8×5.7 μm² and CL=crystal layers at 5.6, 18.7 and 57.8 nm ofencapsulating lipid. FIG. 6 was taken at about the same magnificationand C=crystals at 6×3 μm and 2.8×1.7 μm; CL=crystal layers at 5.8, 19.2,69.2 nm. This and other electromicrographs show crystals with edgelengths ranging from 0.6 to 8 μm. The actual size of the crystals may bemuch larger since they have gone through freeze fracture treatment. Alarge number of CL crystal layers are seen in the EM and in fact, allcrystals seem to encompass these thin layers. Taking total measurementsat about 200 layers of about 20 cross fraction areas of 4electronmicrographs, three main thicknesses of crystal layers are seen:˜6 nm being the thinnest, and the rest are ˜20 and ˜60 nm. There is nocertainty as to the upper limit of how thick and wide are these crystallayers.

The freeze fracture EM results illustrate the manner in which the lipidwas coated. If it is a random process, the EM will not show repeats inthe layering. Since evidence of ordered or structured layers is seen,this suggests that there is an order in which the fatty acids andtriglycerides are aligned as the two components are emulsified andallowed to coalesce in the encapsulation process.

EXAMPLE 8 Complementary Drug Lipid-Tail Design for Lipid Encapsulation

The new drug, 2-lauramide-5-nitrothiazole, is also referred herein asBA3540. As described above, it is chemically synthesized by condensingthe carboxyl function of lauric acid to the amino group of2-amino-5-nitrothiazole. As known to the skilled artisan, activatingagents that may be used to form the amide linkage include many activatedintermediates of lauryl-acyl-halides, lauryl-active esters, such aslauryl-n-hydroxysuccimide ester, and also by activation withcarbodiimadzole and carbodiimide. The general reaction scheme is shownin FIG. 7.

In a typical example, an equimolar ratio (approximately 2.5 moles) oflauric acid is activated with dicyclohexyl-carbodiimide (DCC) in 500 mLof dimethylformamide. After 90 minutes, the insoluble dicyclohexylureaformed is removed by vacuum filtration. The activated lauric acidsolution is then added in approximately 1:1 ratio of the nucleophile2-amino-5 nitro-thiazole in 600 mL of methylene chloride, 60 ml ofpyridine and made up to 3.5 liters with dimethylformamide. The reactionis allowed to proceed for 40-48 hours with shaking, stirring or heatingat 50° C. The product formed is obtained and purified by precipitationand recrystallization in methanol and or acetone. This synthesis schemeis depicted as 2-lauramide-5-nitrothioazole and is a nice needle shapedmicrocrystal. The bulk drug is oatmeal-colored and insoluble in water,sparingly soluble in methanol and more soluble in methylene chloride anddimethylforamide. To promote complete dissolution, the drug has to belightly heated. In fact, the new compound is remarkably stable and itcan be heated in organic solvents of methanol, acetone, methylenechloride and dimethylforamide at 60-80° C. with no appreciabledetriment.

The structural identification was by (1) elemental analysis, (2)UV-spectrum and (3) HPLC. The results of the identification are: C15,H25, N3, O3, Si; 327, Calculated C, 55%, H, 7.6% N, 12.8%, O, 14.7%, S,9.8% Found 56.25%, 7.5%, 12.8%, (O-not determined) and S, 10.02%. lambdasubmax=350 nm. The UV spectra for BA3540 is shown in FIG. 8. The UV maxis dependent on the solvent and is at about 340 nm-350 nm. For the HPLCanalysis shown in FIG. 9, the column was C-18 and the mobile phase wasin acetonitrile and water. The melting point is 136° C. The lipoidalcharacteristic of the drug lowered the melting point quite substantiallyby about 67 degrees as compared to a known aspirin/NTZ conjugate.

Similar synthesis were made with caprylic acid to yield a C-8 adduct andwith salicylic acid to yield nitazoxnide (NTZ).

EXAMPLE 9 Efficacy of BA3540 Against EPM in Horses

Approximately 2 kg of the BA3540, 2-lauramide-5-nitrothiazole, weresynthesized, purified and crystallized. The new drug was encapsulated asin Example 4 with 27% palmitic acid and 73% of Sterotex®. Anillustration of the encapsulated BA3540 product is shown in FIG. 10. Theencapsulated drug was made into horse paste formulation as before andtested in three horses that exhibited clinical signs of EPM.

Case 1: “Chris” is a 7 year old quarter horse gelding. The horse hadataxia with lameness of a nonspecific origin, gave only moderateresistance to forefront crossing and was unstable on both sides tolateral tail pull. The horse was also tested and confirmed withimmunoblot (Western Blot) to be EPM positive. Chris was given daily oraltreatment of the new paste formulation containing lipid encapsulated2-lauramide-5-nitrothiazole for a total of 28 dosings with 25gm/syringe. (On day 22 to 28, the drug was not given and then resumedmedication in the following week).

On day 9, clinical examination, he stumbled behind when trotted. Whenstanding, he constantly shifted his hind feet, but resisted lateral tailpull. On day 15 examination, Chris shifted hindquarters slightly whenstanding, but at a trot he stumbled both hind feet. On day 22examination, Chris resisted lateral tail pull and no longer shiftedhindquarters while standing. He appeared to have improved a full grade.By day 30 examination, he stood relaxed on the firm surface, resistedlateral tail pull and had no apparent muscle wasting. Based on generalEPM grading, Chris went from Grade 3 to Grade 0/1 by the new drug pastetreatment. Owner's observation from day 30 to day 84 indicated that thehorse ate well, played in his paddock, and regained an alert andaggressive attitude. Chris had become apparently sound in health.

Case 2: “Brooke” is an 18-year-old thoroughbred mare. The horse had apositive Western Blot serum test for EPM exposure. She had notable rightforeleg response and failed to resist crossover for brief periods. Alsothere was muscle atrophy and edema of the left hindquarter. The righthindquarter failed to resist lateral tail pull. Her EPM syndrome wasrelated to rapid weight loss, especially on the right hindquarter,affecting stifles as well. Other tests (complete blood count and serumenzyme analyses) indicated an elevation in protein globulins at thebeginning of drug treatment and a return to normal by the end of thetreatment. Again the horse was given daily oral treatments with thecurrent dose of a typical 1000 lb horse at about 50 mg/Kg body weigh or25 gm/day. The mare maintained good appetite for food throughout thetrial.

On day 7 clinical examination, the mare resisted foreleg crossover onboth sides yet she yielded to lateral tail pull from both directions.She had slight left hind toe drag after 2-3 minutes lunge, but nostumbling. The left hind leg was swollen from foot to hock. At day 16examination, muscle loss in the left hindquarter was not as obvious.When lunging clockwise in a circle, she went stiffly and dropped herhead for balance. At day 21, her reaction to lateral tail pull hadchanged; the right hind leg strongly resisted and the left side had onlymoderate resistance. By day 29, there was strong resistance to forelegcrossover. However on lounge she still dropped her head. On gradescoring she started out at a Grade 2 and remains as grade 2 at thattime. From day 29, the mare continued to improve without additionalmedication. She continued to gain weight, attitude, and aggressiveness.By Day 84, according to the owner, she was running and bucking in herpaddock and deemed to be in sound health.

Case 3: “Foundation Man” is a 22-year-old Appaloosa gelding. The horsewas examined by three veterinarians who suspected an infection of equineprotozoal encephalomyelitis based on clinical signs of stumblingrepeatedly on level, familiar ground. The horse had stumbled and fallenwith the rider at a trot in his own paddock. The horse had a positiveWestern blot serum test for EPM exposure. Foundation Man was given dailyoral treatments with the same amount of medication for 28 days. Theclinical signs of note at weekly examinations were: (1). right lowerback muscle spasm and (2). stiffness of motion when lunging clockwise ina circle.

This horse was most responsive to the medication. He maintained anexcellent appetite for food throughout the trial. There was a notableimprovement in energy, aggressiveness, and vigor by Day 15, which hemaintained throughout. Brief stumbles when lunging became lesspronounced to none affecting controlled forward motion in eitherdirection. Lower back spasm was also reduced by day 14 and disappearedthereafter. In response to this, his forward motion became more fluid.Based on general characteristics of EPM grading, Foundation Man wentfrom Grade 2/3 to Grade 0 by 28 day of new drug treatment.

As indicated in the testing described above, the lipid conjugate, BA3540(2-lauramide-5-nitrothiazole) is both efficacious and safe. Unlike NTZ,the drug is palatable and does not cause anorexia, depression,diathermia or loose stool in horses. All three treated horses acceptedthe formulation with no side effects. Almost all horses gained weighteven during the first week of treatment and continued to gain weightduring the 28 days treatment. The three treated horses had diverseneurological symptoms and yet all showed progressive improvements duringthe 28-day treatment period. They continued to improve even after thedrug treatment period with no medication or supplements. Reports fromthe owners indicate that all three horses fully recovered from EPM and ishow no relapse at day 84.

EXAMPLE 10 Efficacy of BA 3540 in Treating Coccidiosis in Chickens

An initial trial involving 120 broilers (4 week old chickens) for thetreatment of coccidiosis was made. Three treatment groups were used: (1)control, (2) low dose of 10 mg BA 3540/kg treatment, and (3) high doseat 50 mg BA 3540/kg treatment. The broilers were separated into sixpens, each with 10 birds. Fecal collection was begun to check for thepresence of coccidian. The treatments were then assigned and the trialstarted. The treatment was added to a mash diet and fed adlib for sevendays. At the end of the treatment period, new fecal collections for eachtreatment group were analyzed for the presence of coccidia.

The drug formulation was accepted by the broilers with no adverse effectand all broilers remained in good health throughout the seven weeks withno mortality. Two fecal samples were taken from each pen and a fecalfloat was done to check oocyst levels. Oocyst levels are considered todetermine the adult coccidian present in an intestinal tract. The levelof coccidia infestation at the beginning of the trial was moderate.

After the seven weeks of treatment, the high dose group (50 mg/kg) onlyhad 1 of 4 samples with detectable oocyst. The drug therefore isefficacious in the high treatment group. In the low treatment group (10mg/kg), the amount of oocyst is about the same as the control group. Theoocyte count is not discriminating enough to differentiate between thelow treatment group and the control group.

A confirmatory trial was conducted with 10 seven-week-old Arbor Acresbroilers. The birds were divided into two groups: control and 50 mg/kgtreatment groups. The two set of cages were off the floor to prevent anypotential contamination. The trial was monitored for four days and fecalfloats for oocyte population were used to determine efficacy. Two fecalsamples were collected from each cage. The control fecal samples showedsimilar levels of coccidial oocytes, while the treatment group showed novisible oocytes.

EXAMPLE 11 Antifungal Activity of BA 3540

The antifungal activity has been demonstrated for NTZ (see U.S. Pat.Nos. 5,578,621 and 3,950,351). These patents suggest that in-vitro yeastand various dematophites are susceptible to nitrothiazole(nitazoxanide). In the present study, patients suffering from yellowfungal toes were treated with a 3% weight percent BA3540 in a gelformulation (gel comprises propylene glycol and 0.8% Carbopol® Gel) for5 consecutive days by topical application of the gel formulation on thesurrounding nail cuticle area, followed by weekly treatment with the gelformulation for the next 4 weeks. The thickening of the nail caused byfungal growth disappeared after two weeks, and several months later ahealthy nail began to appear behind the thick nail.

EXAMPLE 12 Antiviral Activity of BA 3540

NTZ has been described as possessing antiviral activity, andspecifically against Herpes Virus, such as Epstein Barr virus (EBV),Varicella Zoster virus (VZV), Human Simplex virus (HSV) and HumanCytomalovirus (HCMV). A preliminary assessment of anti-HSV and anti-HCMVactivities of BA3540 is made by using NTZ as a positive control.

The drugs, NTZ and BA 3540, were made soluble at 10 mg/mL indimethylsulfoxide and then diluted in media to 50 μg/mL, 5 μg/mL, 2.5μg/mL, and 1.5 μg/mL. Human embryonic fibroblast cells were propagatedin minimal essential media and supplemented with 10% fetal bovine serum.Cells were pre-treated with the two drugs at the 4 specifiedconcentrations plus a zero control for 45 minutes. The plates were eachinfected with 300-400 viral particles of either HSV or HCMV for 1 hour.Drug free media was added to each plate and incubation continued for 3days to propagate virus. At the end of three days, the supernatant fromeach of the plates was removed for plaque reduction assays.

Both drugs were effective as antiviral agents. This is especially truewith respect to HCMV. In controls, there were 300 plaques. BA 3540 at1.5 μg/mL and 2.5 μg/mL showed 3 and 1 plaques, respectively, and noneat the higher drug concentrations. NTZ control showed 310 plaques,whereas there were no viral plaques at all four drug concentrations. Theprojected therapeutic range for BA 3540 is about 1.5-2.5 μg/mL for HCMV.The therapeutic range of BA 3540 with respect to HSV is about 5-10μg/mL. In productively infected HSV control there were 110 plaques,whereas at 1.5 μg/mL there were 90 plaques. The present data establishesthat BA 3540, like NTZ, is effective as an antiviral agent for HerpesVirus.

EXAMPLE 13 Synthesis of BA 11671, N-dodecyl-2-oxazolidinone(N-lauryl-oxazolidinone)

2-Oxazolidinone is a new class of antibiotic marketed under thetrademark, Zyvox®, by Pharmacia Upjohn. It is the first complete newclass of commercialized antibiotics in 35 years. Linezolid tablets andinjectables are for the treatment of gram-positive bacteria andpneumonia caused by methicillin-resistant Streptococcus pneumoniae andStaphylococcus aureus. The core structure of oxazolidinone is afive-member ring. The drug derivatives are built around the corenitrogen at position 3 in the oxazolidinone ring. Hence variouspermutations and combinations of analogs of phenyloxazolidinones havebeen described (U.S. Pat. No. 6,166,056). Obviously, the phenyl ring isnot a prerequisite for activity, because 3-chloro-2-oxazolidinones havebeen shown to exhibit antibacterial activity (U.S. Pat. No. 3,931,213).However, it is known that the (S)-enantiomer is pharmacologicallyactive. The racemic mixture is useful, but will require twice as muchmaterial for the same antibacterial effect. The identification of thiscore structure constitutes the first step in developing a new drugentity for the lipophilization techniques described herein.

A chemical synthetic approach exemplifies the ease with which a newanalog can be generated using the methods described herein. The reactionwas an equal molar condensation of laurel chloride and 2-oxazolidinonein dimethylforamide. Pyridine was used to neutralize the HCl generatedin the condensation of an imide-bond. After the incubation at 50° C. for24 hours, the reactants were diluted with two volumes of methanol andcrystallized in the cold. The new drug, N-(lauryl)-2-oxazolidinone, wasagain recrystallized a second time to ensure purity.

The resultant elemental analysis confirmed the composition of the newanalog. The structural chemical composition is: C15, H27, N1, O3, withthe formula weight of 269. The theoretical composition is: C 67%, N5.2%, H 10.04%, O 17.76%; found, C 66.96%, N 5.23%, H 10.08%, (O-notdetermined). The melting point is 69° C. and is significantly lower thanthat of 2-oxazolidinone (90° C.) because the drug is more lipid-like.

EXAMPLE 14 Synthesis of BA 91346, N-dodecyl-2-methyl-nitroimidazole,(N-(lauryl)-2 methyl-nitroimidazole)

The new drug, BA 91346, is an analog of metronidazole(N-ethanol-2-methyl-5-nitroimidazole). The parent drug is an antibioticused in the treatment of anaerobic bacteria and in particular for thetreatment of ulcer that is caused by the bacteria (Halobactor.pylori).It is also used as an anti-parasitic drug.

Chemical synthesis of BA 91346 involved reaction of lauroyl chloridewith the imidazole group of 2 methyl-5 nitroimidazole indimethylforamide and pyridine. Equal molar of the two reactants aremixed and the reaction is for 24 hours at 50° C. The solution wasdiluted two fold with methanol and chilled to crystallize the compound.After drying, the compound was re-purified by crystallizing frommethanol.

The structural formula of the new compound is C 16, N 3, H 28 and O 3;and the formula weight is 310. Elemental analysis theoreticalcomposition of C, 62%, N, 13.5%, H 9.03%, O 15.47%; found C 62.6%, N13.05%, H 9.08% and O-(not determined). The melting temperature forBA91346 is 74° C. while the parent compound metronidazole is 161° C.Again the observed lower melting temperature is due to lipidization ofthe drug derivative.

EXAMPLE 15 Synthesis of BA 61274,CH₃—(CH₂)₁₁—NH—CO—CH₂—S—CH₂—CH(CH₃)—CO-Pro

The biologically active core structure for Acetocholine EsteraseInhibitor (ACE-Inhibitor) has been described as a dipeptide. InCaptopril, there is one mercapto-functionality that can be exploited forlinkage to a fatty acid. The simplest approach is to react withlauryol-chloride to yield a thioester. Equal molar of captopril andlauroyl chloride are reacted in dimethylforamide and pyridine for 6hours at 40° C. Following the reaction, 20 volumes of methanol and threevolumes of water are added. The conjugate is precipitated in the coldand recrystallized once more in methanol.

The second approach is to use dodecylbromide and the sulfahydryl ofcaptopril to form a thioether linkage. In this reaction equal molar ofthe two reactants are added in dimethyformamide and pyridine at roomtemperature for three days. Following the reaction, methanol and waterare added as before and the product is precipitated and recrystallized.

The above two products form either a thioester linkage, which ishydrolysable, or thioether, which is non-enzymatically cleavable. Forthis reason, a third preferred synthesis option involves the creation ofan amide linker that is hydrolytically stable and yet enzymaticallycleavable. In the reaction, a bifunctional linker bromoacetyl-bromide isemployed. This linker is first attached to the lipid moiety bybromoacetylation. In the reaction, 165 g (1 mole) of n-dodecanoamine isreacted by the slow addition of 222 g (1.1 mole) of bromacetyl-bromideat room temperature for 2 hours in 800 ml of dimethylforamide and 80 mLof pyridine. Following reaction, the precipitated adduct is filtered byvacuum filtration. The product is resuspended in 800 mL of ethylacetateand hexane (1:1) and re-filtered. The product,dodecylamido-acetyl-bromide, has a molecular weight of 306 Da and iscrystalline and white. The conjugation reaction is with 1.42 g ofdodecylamido-acetyl-bromide and 1 g of captopril in 2 mL ofdimethylforamide and 0.25 mL of pyridine for 3 days at room temperature.Following the reaction, 20 volumes of methanol and three volumes ofwater are added. The conjugate is precipitated in the cold andre-crystallized once more in methanol.

1. A biologically active lipophilic composition, comprising asubstituted or unsubstituted 5-nitrothiazole covalently attached to alipid, the lipid being selected from the group consisting of fatty acidsand esters of fatty acids.
 2. The composition of claim 1, wherein thelipid is a C4-C30 fatty acid.
 3. The composition of claim 2, wherein thelipid is a C10-C30 fatty acid.
 4. The composition of claim 1, whereinthe lipid is a fatty acid comprising at least 10 carbon atoms.
 5. Thecomposition of claim 1, further comprising one or more pharmaceuticallyacceptable carriers.
 6. The composition of claim 1, wherein thesubstituted or unsubstituted 5-nitrothiazole covalently attached to alipid is encapsulated in at least one lipid selected from the groupconsisting of fatty acids esters of fatty acids, and mixtures thereof.7. The composition of claim 1, wherein the biologically activelipophilic composition is in solid form and adapted for oraladministration.
 8. The composition of claim 1, wherein the substitutedor unsubstituted 5-nitrothiazole covalently attached to a lipid has thestructure:

wherein L is a linkage, R is hydrogen, alkyl, substituted alkyl, aryl,substituted aryl, heteroaryl, substituted heteroaryl, heterocyclic, orsubstituted heterocyclic, and LIPID is a residue of a C4-C30 fatty acid.9. The composition of claim 8, wherein LIPID is a residue of a C7-C30fatty acid.
 10. The composition of claim 9, wherein LIPID is a residueof a C10-C30 fatty acid.
 11. The composition of claim 8, wherein thelinkage is hydrolytically stable in aqueous solution at physiologic pHand enzymatically cleavable.
 12. The composition of claim 8, wherein Lis selected from the group consisting of ethers, thioethers, imides,amides, sulfonamides, phosphonamides, disulfides, and carbamides. 13.The composition of claim 8, wherein L is —NH—C(O)— or —NH—CH2—C(O)—NH—.14. A biologically active lipophilic composition comprising2-lauramide-5-nitrothiazole.
 15. A method of treating an infection in ananimal, comprising administering a therapeutically effective amount of abiologically active lipophilic composition of claim
 1. 16. The method ofclaim 15, wherein said step of administering comprises administeringorally.
 17. The method of claim 15, wherein the infection is aparasitic, bacterial, viral, or fungal infection.
 18. The method ofclaim 15, wherein the infection is a protozoan infection.
 19. The methodof claim 15, wherein the infection is equine protozoal myeloencephalitis(EPM) or coccidiosis.
 20. The method of claim 15, wherein the animal isselected from the group consisting of humans, horses, and chickens. 21.A method of treating an infection in an animal, comprising administeringa therapeutically effective amount of a biologically active lipophiliccomposition of claim
 8. 22. The method of claim 21, wherein said step ofadministering comprises administering orally.
 23. The method of claim21, wherein the infection is a parasitic, bacterial, viral, or fungalinfection.
 24. The method of claim 21, wherein the infection is aprotozoan infection.
 25. The method of claim 21, wherein the infectionis equine protozoal myeloencephalitis (EPM) or coccidiosis.
 26. Themethod of claim 21, wherein the animal is selected from the groupconsisting of humans, horses, and chickens.
 27. A method of treating aninfection in an animal, comprising administering a therapeuticallyeffective amount of a biologically active lipophilic composition ofclaim
 14. 28. The method of claim 27, wherein said step of administeringcomprises administering orally.
 29. The method of claim 27, wherein theinfection is a parasitic, bacterial, viral, or fungal infection.
 30. Themethod of claim 27, wherein the infection is a protozoan infection. 31.The method of claim 27, wherein the infection is equine protozoalmyeloencephalitis (EPM) or coccidiosis.
 32. The method of claim 27,wherein the animal is selected from the group consisting of humans,horses, and chickens.